The present invention relates to bonding tools for bonding wire leads to a contact. In the manufacture of semiconductor devices one of the steps includes attaching an electrical connection between a contact area on the semiconductor device and a corresponding electrical lead. It is often necessary to make connections between individual circuit elements on the device itself.
One type of prior art bonding tool employs ultrasonic techniques. A so called wedge bonding tool has a bonding tip of about 3 mils on a side which is vibrated against the wire lead to be bonded at ultrasonic frequencies. Extremely high vibrations used in this technique result in the joining of the wire lead to the contact area to which the lead is to be connected. However, this type of bonding does not always yield reliably bonded connections. As a result, undesirable economic losses are incurred in the manufacturing processes due to the failure of these bonds in a portion of a given production manufacturing batch. Such failures need to be detected and screened prior to utilization of the assembled device in its intended environment. This further adds to the cost of production of these devices.
The present invention is directed to the cause of failure of these bonded connections. Ordinarily the bonding tools are manufactured by a grinding technique. It has been found that such manufacturing techniques produce a given surface finish on the bonding tip of the tool. It has been discovered that the cause of the bonding failure is attributable to the particular finish on the bonding bit itself. In essence the tool constructed in accordance with the present invention is provided a surface finish which enhances a mechanical bond between a lead and a mating contact surface and provides longer lasting tools, as well as greatly improved reliability of the bonded product.